In order to increase the resistance of blades to FOD (foreign object damage) in the airflow, that is to say to foreign bodies such as birds and hailstones, they comprise a leading-edge reinforcement, the role of which is to protect the leading edge from damage during impact with an FOD and to distribute the impact force over a large surface area of the blade.
A reinforcement for the blade leading edge conventionally comprises a suction-face fin at least partially covering the aerodynamic suction-face surface of the blade and a pressure-face fin at least partially covering the aerodynamic pressure-phase surface of the blade, these two fins being joined by a leading edge of the reinforcement.
When the blade is able to move with respect to the axis of the turbine engine, it turns its pressure-face surface to the front, that is to say the air comes into contact on the pressure-face surface, thus creating an overpressure on the pressure-face surface and a negative pressure on its suction-face surface.
The impact of an FOD on the leading-edge reinforcement has a tendency to cause a detachment of the upper portion of the pressure-face fin. Beyond a certain mass of FODs, the force of the impacts is greater on the reinforcement, which is also causes a detachment of the upper portion of the suction-face fin. The overpressure generated on the pressure-face tends to limit the detachment of the pressure-face fin to the pressure face. On the other hand, the combination of centrifugal force, greater at the blade tip than at the root, with the negative pressure generated on the suction face, tends to promote the detachment of the suction-face fin.
When the blade is a fan blade mounted in an external fairing carrying an internal abradable layer facing the blades, the detachment of the suction-face fin causes damage to the internal abradable layer. This is because the suction-face fin projects from the suction face of the blade and penetrates the internal abradable layer, which creates a furrow in the internal abradable layer. It is then necessary to immobilise the turbine engine in order to replace both the blade the leading-edge reinforcement of which has detached and the internal abradable layer. Such a mobilisation gives rise to a high cost resulting from the lack of operation of the turbine engine, which it is important to reduce or even eliminate.